Liquid fuel injection systems

ABSTRACT

A fuel injection nozzle includes a valve member movable against the action of resilient loading by means of fuel under pressure supplied from an inlet. The nozzle also includes a piston which is operably connected to the valve member and which is subjected to fuel under pressure flowing by way of a valve controlled conduit. The fuel under pressure acting on the piston reinforces the action of the resilient loading. Conveniently the fuel is obtained from the inlet of the nozzle unit.

ilite States ntent Fenne et all.

[451 Mar. 19, 11974 LIQUID FUEL INJECTION SYSTEMS [75] Inventors: llvor Fenne, Greenford; Douglas Gordon Burton, Weybridge, both of England [73] Assignee: C.A.V. Limited, Birmingham,

England [22] Filed: Oct. 25, 1972 Appl. No.: 300,858

[30} Foreign Application Priority Data Oct. 28, 1971 Great Britain 50066/7l [52] US. Cl. 239/533 [51] Int. CL... F02m 47/00 [58] Fiend of Search 239/533, 96, 94

[56] References Cited UNITED STATES PATENTS 3.610.529 lO/l97l Huber 239/533 X Guegan et al 239/533 X Monpetit et al. 239/533 X FOREIGN PATENTS OR APPLICATIONS 1.242.368 8/1960 France .i 239/533 Primary Examiner--M. Henson Wood, Jr. Assistant Examiner-Michael Y. Mar

[ 5 7 ABSTRACT A fuel injection nozzle includes a valve member movable against the action of resilient loading by means of fuel under pressure supplied from am inlet. The nozzle also includes a piston which is operably connected to the valve member and which is subjected to fuel under pressure flowing by way of a valve controlled conduit. The fuel under pressure acting on the piston reinforces the action of the resilient loading. Conveniently the fuel is obtained from the inlet of the nozzle unit.

5 Claims, 2 Drawing Figures PAIENIEDm 19 1914 SHEET 2 0f 2 Q43 a m LIQUID FUEL INJECTION SYSTEMS This invention relates to liquid fuel injection nozzles for internal combustion engines the nozzle being of the kind comprising a fluid pressure operable resiliently loaded valve member for controlling the flow of fuel through an orifice from a fuel inlet, the inlet in use, being connected to a fuel pump actuated by the engine.

With such an arrangement the force exerted by the resilient loading on the valve member must be a compromise between the desire to obtain satisfactory operation of the nozzle at high fuel pressures as occur when the engine is operating at normal speeds and also at low fuel pressures as occur when the engine is being started.

If the resilient loading on the valve member is high then when the engine is being started, sufficient fuel pressure may not be generated due to leakage to effect opening of the valve member. On the other hand if the resilient loading is low then the operation of the nozzle at normal engine speeds may be impaired.

The object of the invention is to provide a liquid fuel injection nozzle in a simple and convenient form.

According to the invention a liquid fuel injection nozzle of the kind specified comprises a piston opera bly associated with the valve member, a cylinder in which said piston is located, a conduit through which fuel can be supplied to said cylinder at a pressure substantially the same as the pressure of fuel supplied to the inlet, and a non return valve in said conduit and acting to prevent flow of fuel out of said cylinder, tlie'arrangement being such that the force exerted on the valve member increases as the pressure of fuel supplied to the inlet increases.

In the accompanying drawings:

FIG. 1 shows a fuel system for an engine, the system including fuel injection nozzles constructed in accordance with the invention and FIG. 2 shows another example of a fuel injection nozzle constructed in accordance with the invention.

With reference to FIG. 1 of the accompanying drawings there is shown a system for supplying fuel to a compression ignition engine having three cylinders. The system comprises threee injection nozzles disposed to deliver fuel to the combustion spaces or cylinders of the engine respectively, and the injection nozzles are referenced 10, 11 and 12 which is the firing order of the associated engine.

Each injection nozzle is of conventional construction and includes a nozzle body 13 upon which is mounted a nozzle head 14. The nozzle head is provided with a bore in which is located a valve member 15 the valve member being shaped to cooperate with a s eating to control the flow of fuel through an outlet 16. The member is actuated by fuel under pressure and this is delivered to a chamber 17 disposed adjacent the outlet through a fuel inlet 18. The fuel inlets 18 of the nozzles are connected to a pump means 9 which supplies fuel to the nozzle units in the order appropriate to the firing order of the engine. Thus with reference to the drawing the nozzle will receive fuel first followed by the nozzle 11 and then the nozzle 12.

The valve member of each nozzle is biased towards its seating by means of a coiled compression spring 19 which is located within a spring chamber 20 defined in the body part. Extending from the spring chamber towards the bore accomodating the valve member 15 is an axial drilling in which is located a push rod 21. The push rod 21 bears against the valve member at one and at its other end it mounts an abutment for the spring The spring chamber 20 is vented to a drain so that any fuel under pressure which leaks past the valve member and the wall of the bore in which it is mounted, can flow to the drain.

The spring abutment also mounts a piston 21 and this is slidably located within a cylinder 22 formed in the body part. The end of the cylinder remote from the valve member communicates with a valve controlled conduit 23. The spring loaded valve element of the valve is arranged to prevent the escape of fuel from the cylinder. The area of the piston exposed to the pressure in the conduit 23 is less than the area of the valve member 15 which is exposed to the pressure of fuel at the inlet 18.

The conduit 23 of nozzle 11 is connected to the fuel inlet 18 of the nozzle 10, the conduit of nozzle 12 is connected to the fuel inlet of nozzle 11 and the conduit of nozzle 10 is connected to the fuel inlet of nozzle 12.

In operation and assuming that fuel under pressure is being supplied by the pump means to nozzle 10, the valve member therein will be lifted to permit fuel to fiow through the outlet thereof to the associated combustion space. At the'same time fuel under pressure will be supplied to the cylinder'22 of the nozzle unit 1 l and the peak pressure pertaining in this cylinder will be the peak pressure which occurs during the delivery of fuel to nozzle 10. When fuel is next delivered by the pump means, this fuel will flow to nozzle 1 l and therefore the cylinder 22 of the nozzle 12 will be charged at the peak pressure pertaining during the flow of fuel to nozzle 11. This peak pressure will be greater because a greater pressure of fuel will be required to effect opening of the valve member 15 of the nozzle 11 owing to the fact that the piston 21 thereof is being subjected to the peak pressure which occured during the supply of fuel to the nozzle 10.

The effect of providing the piston 21 which is subjected to pressure in the manner described is to allow the system to start operation from rest with a fairly low nozzle opening pressure and in this manner excessive leakage of fuel in the system which is detremental when starting the engine is minimised. As the speed of operation of the engine increases however the nozzle opening pressure increases and this has the effect of reducing the injection period with resultant advantages in the operation of the engine.

It will be appreciated that the nozzle opening pressure does not continue to increase as described above instead an equilibrium is established since an increase in the nozzleopening pressure does not cause an equivalent increase in the peak injection pressure nevertheless the nozzle opening pressure is related to the speed of operation and the quantity of fuel which is supplied by the pump means. In the particular example the nozzle opening pressure due solely to the spring 19 is atmospheres and the nozzle opening pressure at the cranking speed of the engine is l 15 atmospheres, The nozzle opening pressure at the peak line pressure. that is to say the pressure of fuel supplied by the pump means, is 370 atmospheres, the line pressure being 600 atmospheres.

FIG. 2 shows an alternative arrangement in which like reference numerals are used wherever possible. In this arrangement the piston 24 is located next to the valve member and engages same in end to end relationship. The piston defines the abutment for the spring 19 and the space surrounding the junction between the piston and valve member is vented to a low pressure. The cylinder is extended to define a spring chamber which is in communication with the inlet 18 by way of a valve controlled conduit 25, the valve element of the valve being positioned to allow fuel from the inlet to flow into the spring chamber but to prevent escape of fuel therefrom. As in the previous example the pressure of fuel acting on the piston assists'the action of the spring and the effect is substantially the same as the previous example. In this case however each injection nozzle is complete in itself and requires only the conventional connection to the fuel pump and drain.

The leakage of fuel from the cylinder 22 past the piston 21 shown in FIG. 1 or past the piston 24 shown in FIG. 2, in both cases to drain, allows the backing pressure to drop when the engine speed is reduced.

We claim:

1. A liquid fuel injection nozzle of the kind comprising a nozzle body, a bore formed in the body, a cylindrical valve member located in the bore, a seating at one end of the bore, the valve member being shaped to cooperate with the seating, 21 fuel inlet in the body, a passage connecting said inlet with said one end of the bore whereby when fuel under pressure is supplied to said inlet a force will be developed on the valve member acting to move the valve member away from the seating, an outlet from said one end of the bore and through which fuel can flow when the valve member is lifted from the seating, resilient means acting to urge the valve member onto the seating, a piston operably associated with the valve member, a cylinder in which said piston is located, a conduit through which fuel can be supplied to said cylinder at a pressure substantially the same as the pressure of fuel supplied to the inlet, the pressure of fuel in said cylinder acting on said piston to apply a force to said valve member in a direction to maintain the valve member on the seating, the area of the piston exposed to the fuel pressure in the conduit being less than the area of the valve member exposed to the fluid pressure at the inlet, and a non-return valve in said conduit and acting to prevent fuel flow out of said cylinder, the arrangement being such that the force exerted on the valve member and acting to urge the valve member onto the seating varies as the pres sure of fuel supplied to the inlet varies.

2. A nozzle according to claim 1 in which said conduit communicates with said inlet.

3. A nozzle according to claim 1 in which the. conduit is adapted for connection to an external source of fuel under pressure.

4. A nozzle according to claim 3 in which said resilient means is a coiled spring located within a spring chamber defined in the body.

5. A fuel system for an internal combustion engine comprising a plurality of nozzles as claimed in claim 3, a fuel pump for supplying liquid fuel to the nozzles in turn, each nozzle having its conduit connected to the inlet of another of the nozzles of the system. 

1. A liquid fuel injection nozzle of the kind comprising a nozzle body, a bore formed in the body, a cylindrical valve member located in the bore, a seating at one end of the bore, the valve member being shaped to co-operate with the seating, a fuel inlet in the body, a passage connecting said inlet with said one end of the bore whereby when fuel under pressure is supplied to said inlet a force will be developed on the valve member acting to move the valve member away from the seating, an outlet from said one end of the bore and through which fuel can flow when the valve member is lifted from the seating, resilient means acting to urge the valve member onto the seating, a piston operably associated with the valve member, a cylinder in which said piston is located, a conduit through which fuel can be supplied to said cylinder at a pressure substantially the same as the pressure of fuel supplied to the inlet, the pressure of fuel in said cylinder acting on said piston to apply a force to said valve member in a direction to maintain the valve member on the seating, the area of the piston exposed to the fuel pressure in the conduit being less than the area of the valve member exposed to the fluid pressure at the inlet, and a non-return valve in said conduit and acting to prevent fuel flow out of said cylinder, the arrangement being such that the force exerted on the valve member and acting to urge the valve member onto the seating varies as the pressure of fuel supplied to the inlet varies.
 2. A nozzle according to claim 1 in which said conduit communicates with said inlet.
 3. A nozzle according to claim 1 in which the conduit is adapted for connection to an external source of fuel under pressure.
 4. A nozzle according to claim 3 in which said resilient means is a coiled spring located within a spring chamber defined in the body.
 5. A fuel system for an internal combustion engine comprising a plurality of nozzles as claimed in claim 3, a fuel pump for supplying liquid fuel to the nozzles in turn, each nozzle having its conduit connected to the inlet of another of the nozzles of the system. 